1. Field of the Invention
The invention relates to a method and apparatus for liquid treatment of wafer-shaped articles, and more particularly relates to improved thermal management of wafer processing by utilizing heated gas to impart heat to a wafer-shaped article principally by convective heat transfer.
2. Description of Related Art
Liquid treatment includes both wet etching and wet cleaning, wherein the surface area of a wafer to be treated is wetted with a treatment liquid and a layer of the wafer is thereby removed or impurities are thereby carried off. A device for liquid treatment is described in U.S. Pat. No. 4,903,717. In this device the distribution of the liquid may be assisted by the rotational motion imparted to the wafer.
As the wafer diameter increases, so too will the temperature differential between a liquid at the point where it is applied in a central region of the wafer and the same liquid after it has travelled radially outwardly to the periphery of the wafer. Such temperature differentials can contribute to damage to the device structures formed on the wafer, for example the damage phenomenon termed “pattern collapse.”
The problem of pattern collapse becomes more serious as the aspect ratio of the submicroscopic structures continues to increase. This is also an ongoing trend in the manufacture of semiconductor devices, as the pressure to reduce device dimensions in general applies more to the horizontal layout and less to the thickness direction.
Conventional apparatus are equipped with infrared, LED or conductive heaters for heating a wafer so as to promote a uniform temperature distribution across the wafer surface. However, with IR heaters the heating is sensitive to wafer type, and may cause photo-corrosion of the traces in the wafer. Moreover, processing chemistries can be light sensitive, as well as components of process module. Additionally, very high temperatures of the heater filament are a safety concern.
With LED heaters, heating is also sensitive to wafer type, and the light sensitivity of processing chemistries and components of the process module area again of concern. Furthermore, the very high power densities of the individual LEDs can be challenging to cool effectively.
Conductive heaters are not thermally effective without a coupling fluid, and thermal mass is a concern.